1. Field of the Invention
The present invention relates to cleaning tools for wells. More particularly, the present invention relates to method and apparatus for providing cavitation and cleaning tool for wells in coal bed methane industry.
2. Description of the Related Art
In coal mining industry, a device called an under-reamer is used to clean and flush out old coal mining wells that are not in active production. Generally, the wells are opened from 6 to 24 inches in diameter and the under-reamer is used for completion and work-over type operation. Once the wells are cleaned and flushed out, they can be put back in the production line. The under-reamer is approximately 36 inches in length, and has a 4-inch body with several 5-inch blades that are configured to protrude away from the body with applied air pressure.
FIGS. 1A-1C illustrate an under-reamer 100 for cleaning and flushing out coal mining wells available from Baker Hughes Tool Company. As can be seen, in FIG. 1A, the under-reamer 100 is shown with three blades 110 (third not shown) in a closed position, while in FIG. 1B, the blades 110 are shown in an open position. Moreover, it can be seen from FIG. 1C that a drill bit 50 can be connected to the end of the under-reamer 100 depending upon drilling needs and requirements.
In operation, the under-reamer 100 is tripped in the hole within the well with a 6xc2xc inch bit drill to drill out the cement and the shoe, where the shoe refers to the bottom portion of the casing outlining the inner walls of the well. For example, the casing may be set at one thousand feet in which case, the shoe of the casing would be at one thousand feet depth. Then, cement is forced down the inside of the casing which, in turn, forces the cement up a back side of the casing to extract the cement to the surface of the well. This is generally performed in order to comply with the governmental regulations for the protection of the shallow water sands.
For a coal section of 1,000 feet by 1,000 feet, the section from 1,000 feet to 1,150 feet is drilled out which includes the drilling of a 50 feet rat hole beneath the desired coal section, thus resulting in a total depth of 1,150 feet. Then Gam-Ray log is performed to determine the location of the best coal production after the trip out of the hole. Thereafter, the under-reamer is run to open the hole below the 7-inch casing from 7 to 10 inches from 1,001 feet to 1,100 feet. Then the 10-inch under-reamer is tripped out of the hole and a 14-inch under-reamer is used to open the hole to 14 inches. Having opened the hole to 14 inches, the 14-inch under-reamer is tripped out and a 6xc2xc inch bit is used to trip in the hole, and blows and clean the well with air and drilling foam.
The operation described above may take three to seven days, since in using the bit, the air and drilling foam is jetted straight up and down in a substantially straight line perpendicular to the surface. Furthermore, in using the under-reamer as described above, the excess fine coal tends to get trapped n the cavity of the well bore, and thus the fine coal tends to stay in the well.
More significantly, during the operation of the under-reamer, when air pressure is removed, there are occasions when the two blades do not close. For example, in running the under-reamer through the inside of a 7-inch casing, the 5-inch blades, which, with the applied pressure open to 14 inches, may collect unwanted physical objects behind the blades such that when the applied pressure is removed, the blades do not properly close, requiring approximately two to three hours devoted solely to close the blades on the under-reamer. At a rig time cost of $210 per hour, the extra two to three hours would add an additional cost of $420 to $630.
While the precise cost involved in using an under-reamer may vary depending on the condition of the well as well as other factors, as an illustration, the total cost would include a half-hour trip into the well at $105.00 of rig time, $175.00 for the cost of the under-reamer itself, one hour of rig time at $210/hour, a half-hour trip out cost at $105.00 and a cost for trip in with a bit at $105, totaling to $700.00. Furthermore, if the blades of the under-reamer do not close as discussed above, a substantial amount of time must be devoted to get the blades closed.
In view of the foregoing, in accordance with the present invention, there is provided a cavitation and cleaning tool and a corresponding method of providing the same without any blades and which is configured to open holes in the well of 20 to 24 inches in diameter. Using air and injecting ten gallons of water per minute with one quart of liquid drilling form every 30 minutes, the cavitation and cleaning tool of the present invention is configured to perform a cutting action with the pumped air and water, while the liquid drilling foam acts as a lifting agent for lifting the coal out of the hole. In this manner, the fine coal is maintained in a turbulent motion and the well is cleaned out in a significantly improved manner as compared to using a conventional under-reamer running a bit with a straight up and down circulation motion.
A cavitation and cleaning tool in accordance with one embodiment of the present invention includes an elongated body having a first end, a second end and an outer surface, a hollow channel running between said first and second ends defining an inner surface of said body, said body including a plurality of ports positioned at a predetermined distance from each other on said body, each of said ports connected to said hollow channel, wherein when pressure is applied at said first end of said body in said channel, each of said ports configured to pass the content of said channel through said each port in a radial direction substantially perpendicular to said outer surface of said body.
In one aspect of the present invention, the body and the hollow channel are substantially cylindrically shaped, where the channel defines a substantially circular openings at the respective first and second ends of the body, each of the substantially circular openings having a diameter of approximately 4.5 inches. Furthermore, each of the ports has a substantially cylindrical port channel each connected to the hollow channel of the body for passing the content therethrough, where the port channel each has approximately a one-inch diameter. Moreover, each of the plurality of ports is positioned substantially equidistant from each other at approximately a 90 degree angle.
Furthermore, in accordance with one aspect of the present invention, a predetermined portion of the inner surface of the body at the first and second ends are each threaded, where the threaded predetermined portions are 3xc2xd inches each in length along the length of the inner surface of said body. Furthermore, the content passed through the hollow channel of the body and each port channels includes a combination of water, air and drilling foam, where when the pressure is applied at the first end of the body in the channel, the body is configured to rotate while passing the content of the channel through each of the plurality of ports.
A method of providing a cavitation and cleaning tool in accordance with another embodiment of the present invention includes the steps of providing an elongated body having a first end, a second end and an outer surface, a hollow channel running between said first and second ends defining an inner surface of said body; providing a plurality of ports at a predetermined distance from each other on said body, each of said ports connected to said hollow channel; and applying a pressure at said first end of said body in said channel to pass the content of said channel through said each port in a radial direction substantially perpendicular to said outer surface of said body. Moreover, in accordance with the present invention, the method of providing the cavitation and cleaning tool may further include the steps of rotating said body and passing the content of said channel through each of said plurality of ports.
These and other features and advantages of the present invention will be understood upon consideration of the following detailed description of the invention and the accompanying drawings.